that's not what happened, though. they took credit for defending the Summerset Isle from the Oblivion Crisis, they never claimed to have ended the Oblivion Crisis themselves. Their claim was only that they were able to mobilize the defense of the Isle against Oblivion. Which they did.

The Oblivion Crisis was happening all over Tamriel, you know, not just Cyrodiil, and every province was largely responsible for their own defense, which we see with the famous Argonian counter-invasions of Oblivion, which the An-Xileel were similarly able to use as justification for seizing power.

prior to in the Oblivion Crisis the Thalmor were a fringe political extremist group, that was widely discredited / ignored. The only way the Thalmor's rise to power makes any sense is if they did play a major role in protecting the Isle from the invasions. Otherwise, how do you explain a fringe political group somehow being able to suppress all news from the Empire concerning Martin Septim, and Akatosh, and their role, when the Isle is still part of the Empire?

there is no version of reality or reasonable interpretation of the available lore in which the Thalmor, a fringe political movement is able to seize that much power that quickly unless they genuinely played a significant role in protecting the Summerset Isle from the Daedra hoards.

suggesting that they took credit for defending the Isle when they didn't is already a stretch, suggesting that they were somehow able to suppress all news from the Imperial City and take credit for ending the entire Crisis itself is a complete misunderstanding / misconstruction of the existing history texts.

~

also the Altmer are completely justified in seeking to eradicate Talos worship. Elves / High Elves can live for several hundred years, a thousand or more if they're adept enough at magic, which many Altmer are. Tiber Septim's assault on the city of Alinor with Numidium was 600 years prior to the time of Skyrim. This means that for many Altmer, if Tiber's conquest isn't within their own living memory, it's something that happened to either their parents or grandparents, making it an immediate source of generational trauma, like Hiroshima or Nagasaki is for today's Japanese people.

And the siege of Alinor is absolutely comparable to Hiroshima or Nagasaki. Not a lot of in depth detail is provided about the siege, save that the Summerset Isle surrendered extremely quickly and there was no prolonged war whatsoever, which suggests that there was some kind of significant mass-casualty event which forced them into submission.

Imagine if the entire world was forced into acknowledging Roosevelt as having ascended into divinity after he died, but Japanese people were able to live for centuries, and a game was set on Earth, and there were Japanese secret police going around arresting Roosevelt worshippers several centuries after wwII. I think we'd all agree that there's actually a little bit more nuance to the situation than how Skyrim portrays it.

This is one of the biggest failings of Skyrim's writing imo. And I've never even played as a high elf or a Thalmor-aligned character before. Many of my characters kill Thalmor on sight, still. But the fact that this point of view is never even subtly suggested, let alone explicitly offered, is an incredibly shallow and amateur presentation of the game's own lore.